BEIJING - China suspended military exchange visits with the United States on Saturday in protest over $6.4 billion in planned US arms sales to Taiwan and warned the US ambassador that the sales would harm already strained ties. The state-run Xinhua News Agency cited the Defense Ministry as saying the suspension is due to the "severe harm" of the arms sales on the two countries' military relations. China took a similar step in 2008 after the former Bush administration announced a multibillion-dollar arms sale to Taiwan ��" the most sensitive issue in US-China relations. The latest arms sales could complicate the cooperation the US seeks on issues ranging from Iran's nuclear program to the loosening of Internet controls, including a Google-China standoff over censorship. China claims the self-governing Taiwan as its own, while the United States is Taiwan's most important ally and largest arms supplier. The US government is bound by law to ensure the island is able to respond to Chinese threats. Though Taiwan's ties with China have warmed considerably since Taiwanese President Ma Ying-jeou took office 20 months ago, Beijing has threatened to invade if the island ever formalizes its de facto independence. China has more than 1,000 ballistic missiles aimed at Taiwan. The arms sale, posted Friday on a Pentagon Web site, includes Black Hawk helicopters, Patriot Advanced Capability-3 missiles, mine hunter ships and information technology. Congress has 30 days to comment before the plan goes forward. Lawmakers traditionally have supported such sales.